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Introductory Chapter: Marine Ecology—Biotic and Abiotic Interactions

This investigation focused on weekly variations in cell density and volume of the dinoflagellateNoctiluca scintillans between March 2001 and January 2004 in the Dardanelles. March-June andOctober-December periods were excessive bloom periods. During the bloomperiods the density of N. scintillans reached 2.20 × 105 cells L-1 witha volume of 1.32 × 1012 µm3 L-1. In addition tothe high surface density, there was an increase in subsurface waters duringthe blooms. The bloom of N. scintillans, like that of diatom and otherdinoflagellate blooms, was associated not only with eutrophication, but alsowith stable temperatures and salinities.

Coccolithophores have had an effect on global climate change for a few million years. The marine phytoplankton group is responsible for approximately 20% of the total carbon fixation in marine systems. They can form blooms spreading hundreds of thousands of square kilometers, are recognized by elegant coccolith structures formed from calcium carbonate exoskeletons, and are visible from space. Although carbon is transferred to the sediments in organic matter and calcite form by coccolithophores, carbon dioxide (CO2) is released by the calcification process. Therefore, they have a complex effect on the carbon cycle due to their activity regarding CO2 production and consumption. This review represents the first attempt to present temporal and vertical distributions of Emiliania huxleyi (Lohmann) Hay & Mohler, 1967 (Ehux), which is one of the most important species of the coccolithophores in the bloom periods and the interaction of this species with other phytoplankton groups in the Sea of Marmara. This study may also indicate the advance of this species from the Black Sea region through the Sea of Marmara and the Dardanelles under favorable conditions.

This study was carried out to determine the short time series of phytoplankton density and chlorophyll a in relation to nutrients and other environmental parameters in surface waters of Kepez harbor in the Dardanelles in winter period of 02 December 2004 and 07 March 2005. Average temperature, salinity, pH, specific conductivity, TDS, DO, TSS, NO- 2+NO- 3, PO-34, SiO4 and chlorophyll a were measured 9.47°C, 27.5 ppt, 8.12, 42.86 mS cm-1, 27.86 g L-1, 9.23 mg L-1, 27.1 mg L-1, 0.43 ìM, 0.23 ìM, 2.91 ìM, 1.919 ìg L-1, respectively. Both N:P (1.78) and Si:P ratios (14.9) were significantly lower than the assimilatory optimal Redfield ratio. Total phytoplankton density varied between 8.25E+04 and 4.71E+06 Cell L-1. Phytoplankton community structure was observed to be controlled by 3 dinoflagellates and 4 diatoms in the Dardanelles. However, there also were blooms of coccolithophoride Emiliania huxleyi in early December (2.36E+06 Cells L-1) and late February (1.57E+06 Cells L-1) and some silicoflagellates such as Dictyocha spp. in early February (2.36E+05 Cells L-1). Contribution of diatoms to total phytoplankton density (48.8%) was higher than the contribution of dinoflagellates (30.9%) and other taxonomic groups (20.3%). Relationships between chlorophyll a and diatoms (r=0.726), between chlorophyll a and dinoflagellates (r=0.579) and between chlorophyll a and other taxonomic groups (r=0.514) showed that chlorophyll a was highly controlled by diatoms than dinoflagellates and other taxonomic groups. On the other hand, short time distribution of phytoplankton revealed that there was growing 7 phytoplankton populations in the winter period. High chlorophyll a, nutrient, phytoplankton density and rational differences between major taxonomic groups revealed that the Dardanelles was connected with the process of eutrophication due to high terrestrial discharges coming from Black Sea surface waters via straits system and international carrying activities by vessels.

This study concentrated on temporal distribution and species composition of phytoplankton connected with physicochemical variations between January 2003 and November 2004 in the South Western Caspian Sea. During the study, 75 phytoplankton were distinguished in total and average phytoplankton densities in 2003 and 2004 were 1.47×10±6.05×10and 1.97×10±7.18×10 cells L, respectively. Contributions of diatoms (66.0% in 2003; 57.0% in 2004) and cyanophytes to total phytoplankton (17.0 in 2003; 36.0% in 2004) were higher than any other group. Diatoms Dactyliosolen fragilissimus and Thalassionema nitzschioides, and cyanophytes Oscillatoria sp. and Anabeanopsis raciborskii provided the biggest contributions to the total phytoplankton. Average DIN concentration in 2003 was higher (3.86±1.65 µM) than the average in 2004 (3.37±1.13 µM). However, average DIP concentration in 2003 was lower (1.45±1.37 µM) than the average in 2004 (1.99±0.67 µM). Average DIS concentration was two-fold higher than average DIN concentration. Average DIN:DIP without NH (2.66±1.66 in 2003; 1.69 ± 1.17 in 2004) and DIS:DIP ratios (5.61±3.44 in 2003; 3.93±2.49 in 2004) were clearly lower than Redfield ratios. Nutrient ratios and phytoplankton densities revealed that system was eutrophic, Bu çalışmada, Güney Batı Hazar Denizinde fiziksel ve kimyasal değişimlerle ilişkili olarak Ocak 2003 – Kasım 2004 döneminde zamana bağlı fitoplankton değişimleri ve fitoplankton tür kompozisyonu incelenmiştir. Çalışma süresince, toplam 75 fitoplankton türü tanımlandı ve 2003 ve 2004’deki toplam fitoplankton yoğunlukları sırasıyla 1,47×10±6,05×10 ve 1,97×10±7,18×10 hücre L olarak bulundu. Diyatomelerin toplam fitoplanktona olan katkıları (2003’de 66,0%; 2004’de 57.0%) ile siyanofitlerin toplam fitoplanktona olan katkıları (2003’de 17,0%; 2004’de 36,0%) diğer grupların katkılarından daha yüksekti. Diyatomelerden Dactyliosolen fragilissimus ve Thalassionema nitzschioides; siyanofitlerden Oscillatoria sp. ve Anabeanopsis raciborskii toplam fitoplanktona en büyük katkıyı sağladılar. 2003’deki ortalama DIN konsantrasyonu (3,86±1,65 µM) 2004’deki konsantrasyonundan (3,37±1,13 µM) daha yüksekti. Bununla birlikte, 2003’deki ortalama DIP konsantrasyonu (1,45±1,37 µM) 2004’deki ortalama DIP konsantrasyonundan (1,99±0,67 µM) daha düşüktü. Ortalama DIS konsantrasyonu ortalama DIN konsantrasyonundan iki kat daha yüksekti. NH olmaksızın ortalama DIN:DIP (2003’de 2,66±1,66; 2004’de 1,69±1,17) ve DIS:DIP oranları (2003’de 5,61±3,44; 2004’de 3,93±2,49) açık bir şekilde Redfield oranlarından düşüktü. Nütrient oranları ve fitoplankton yoğunlukları ile ilgili sonuçlar sistemin ötrofik olduğunu göstermiştir.